The present invention relates, in general, to wireless communication systems, and more particularly, to an apparatus, method and system for mobile wireless communication hand-off utilizing shared directory numbers and ISDN multiway capabilities.
Mobile wireless communication systems typically employ many base stations (such as cell sites) to provide wireless communication throughout a given geographic region. As a mobile unit may traverse the geographic region, the communication to and from the mobile unit may occur through one or more of these base stations. To maintain an ongoing communication session during such transitions between base stations, various hand-off methods have evolved to transfer the wireless communication to the mobile unit from one base station to another base station, while maintaining such an ongoing call or session.
In the prior art, for some of the various methods utilized during such hand-offs, the communication session may suffer from some degree of interruption, which may be noticeable to the consumer of wireless communication services. As a consequence, a need remains to provide for comparatively seamless hand-offs, which do not interrupt ongoing communication sessions and which are imperceptible to the consumer.
In addition, while other prior art systems may provide comparatively seamless hand-offs, such hand-offs typically utilize considerable network resources. In an Autoplex(copyright) system, for example, in addition to switches and base stations, another network entity referred to as an Executive Call Processor (xe2x80x9cECPxe2x80x9d) selects a server at the new cell site, while another network entity referred to as a Call Processing Database Node (xe2x80x9cCDNxe2x80x9d) transmits various data link messages to the current and new cell sites, adding an additional path to the existing call, directing the new cell site to activate a wireless voice link, and directing the current (serving) cell site to direct the mobile to retune to the new wireless voice link at the new cell site.
As a consequence, a need remains for a wireless communication system to provide comparatively seamless and imperceptible hand-offs. In addition, such a wireless communication system should be reasonably efficient and capable of cost-effective implementation, eliminating or minimizing the use of additional network resources.
The wireless communication system of the present invention provides virtually seamless and imperceptible hand-offs of communication sessions of mobile units. The various embodiments of the present invention are reasonably efficient and capable of cost-effective implementation in existing communication equipment such as switches and base stations. Moreover, the various embodiments of the present invention eliminate or minimize the use of additional network resources such as ECPs and CDNs, while being compatible with other intelligent network devices and systems.
In accordance with the present invention, an apparatus, method and system are provided for hand-off of a communication session utilizing shared directory numbers and multiway capabilities, in which the communication session of a mobile unit is transferred from a serving base station to a target base station. The preferred system includes a switch coupled to a serving base station and a target base station, preferably over digital lines having multiple, independent channels, such as Integrated Services Digital Network (xe2x80x9cISDNxe2x80x9d) lines. Typically, each of the various base stations include a plurality of terminals which handle and process the communication sessions with mobile units and, in general, one or more terminals are assigned directory numbers (xe2x80x9cDNsxe2x80x9d). In accordance with the present invention, such DNs are shared by terminals in the serving base station.
In accordance with the present invention, the serving base station contains a plurality of terminals, of which two or more share a directory number. In general, the communication session to be handed off is occurring on a first call path of a first terminal that has a shared directory number. When a hand-off of the communication is indicated, a second terminal of the serving base station having the same shared directory number (of the first terminal providing the communication session), initiates a second call path to the target base station. This second call path (of the second terminal of the serving base station) is then bridged into the active communication session of the first call path (of the first terminal of the serving base station) to form a multiway communication session among the mobile unit, the two terminals of the serving base station, and via the switch, the target base station. This multiway communication session includes a bridged call path to the target base station. The mobile unit then communicates with the target base station for continuation of the communication session through the bridged call path. The first and second terminals of the serving base station are then released from the call, with the communication session continuing, uninterrupted, over the bridged call path and between the target base station and the mobile unit.
As a consequence, the communication session of the mobile unit has been handed off, seamlessly and without interruption, from the serving base station to the target base station. Such a hand-off has also occurred utilizing minimal network resources, the switch and the base stations, without involvement of other intelligent or supervisory network elements.
The multiway communication session from the serving base station to the switch is established through the transmission of various messages between the serving base station and the switch. The switch is correspondingly configured to establish and connect the second call path to the communication session of the first call path, to form the multiway communication session, upon receipt of these various messages. In one of the embodiments, the serving base station includes instructions to transmit a call set up message to the switch, and to transmit various other messages with reference to the shared directory number and the various first and second call paths.
Numerous other advantages and features of the present invention will become readily apparent from the following detailed description of the invention and the embodiments thereof, from the claims and from the accompanying drawings.